Phaethon was born as the youngest child and only son of Helios and Clymene, who had seven older daughters known as the Heliades. Helios had left to return to his godly duties shortly after Phaethon's birth. Clymene told her son stories about Helios.
As Phaethon grew up, Clymene was overprotective of him and wouldn't allow him to take part in sports at school, which resulted in him not having many friends. When he was sixteen, Phaethon came upon Prince Epaphos showing off his new chariot to a crowd. When Phaethon criticized the chariot, saying that his father's was better, Epaphos demanded proof from Phaethon that he was indeed the son of Helios.
After arriving home, Phaethon told his mother that he wished to see his father, and was told to go to his palace. Phaethon traveled to Helios' palace and met his father and asked to ride his Sun Chariot, which Helios reluctantly agreed to. However, when Phaethon tried to show his playmates he was unable to control the chariot's horses and ended up setting the Earth ablaze. It involved scorching the African plains to desert, giving the North freezing snow, creating several constellations, massive deaths and possibly even turning the African peoples' skin dark.
Appalled at the incident, Zeus used one of his powerful lightning bolts to blast Phaethon out of the chariot, killing him. His body then hurled into the river Po, where it was found by his sisters, who mourned his death and were turned into amber-teared poplar trees. Several years later, Jason and the Argonauts found his body still smouldering with the his crying sister trees around him. They comment on how, compared to them, Phaethon got off easy.
Phaethon is described as the image of a demigod. He was tall and muscular, with the upright bearing of a charioteer. He had bronze skin, curly dark hair, and a regal face.